1. Field of the invention
This invention relates to multilayered containers being excellent in food keeping performances due to their high gas barrier properties, particularly to containers excellent in performances for storing retorted foods.
2. Description of the prior art
Ethylene-vinyl alcohol copolymer resin (hereinafter sometimes referred to as EVOH) is a thermoplastic resin having a high gas barrier property, and is used for containers for storing a wide variety of foods. However, for containers which are subjected to retort sterilization, i.e. sterilization in a hot water having a high temperature of at least 100.degree. C., particularly at 105.degree. to 135.degree. C., under high pressure, there having been a problem that the gas barrier property decreases due to moisture absorbed into EVOH by the treatment. Blending of inorganic powder such as mica into a resin to increase its gas barrier property has been proposed. For example Japanese Pat. Publication No. 32939/1982 disclosed that the oxygen permeability of polypropylene (hereinafter sometimes abbreviated as PP) blended with 30% of mica is lower than that of PP not blended therewith. Plastic Technology (December 1987, pages 77 to 79) describes that incorporation of mica into EVOH improves the gas barrier property, Japanese Pat. Application Laid-Open No. 148532/1987 disclosed a gas barrier film comprising a blend of a thermoplastic resin such as EVOH, and mica. Further, Japanese Pat. Publication No. 22327/1983 disclosed that molded articles having excellent mechanical properties are obtained by melt molding a composition comprising EVOH and mica, and Japanese Pat. Application Laid-Open Nos. 11335/1988 and 11336/1988 disclose that multilayered structures can be obtained by laminating a layer comprising a thermoplastic resin incorporating mica with a layer of another thermoplastic resin.